Capacitation involves changes in the plasma membrane over the sperm head and therefore may lead to sperm release by eliminating or modifying binding molecules on the head. Hyperactivation may provide the force necessary for overcoming the attraction between sperm and oviductal epithelium. Smith and Yanagimachi reported that hamster sperm that had undergone both capacitation and hyperactivation in vitro did not bind to epithelium when infused into hamster oviducts. buy antibiotics online
While using transillumination to study motile sperm within oviducts removed from mated mice, we noted that only hyperactivated sperm detached from epithelium. Also, when bull sperm were capacitated by treatment with heparin in vitro, their binding to explants of oviductal epithelium was reduced. In this case, hyperactivation was not observed. Therefore, we propose that changes in the sperm head surface are responsible for loss of binding affinity, although the pull produced by hyperactivation may enhance the ability of sperm to release themselves. While the binding sites present on the epithelium may not be reduced in number or affinity, epithelial secretions initiated by signals of impending ovulation could enhance sperm capacitation, thereby effecting sperm release.